1. Field of the Invention
This invention relates to apparatus which facilitates Tungsten Inert Gas (TIG) welding but which is neither electrically nor mechanically connected to the TIG welding torch.
2. Description of the Prior Art
Welding filler wire feeder systems are known, operating to feed "hot" or "cold" welding filler wire to the weld puddle at the workpiece. (A "hot" welding filler wire is one which carries a current and serves as a consumable electrode. In hot wire systems, the welding arc is struck between the workpiece and the consumable electrode with a high voltage potential difference existing between the workpiece and the consumable electrode. Many hot wire welding processes are of the Gas Metal Arc type, commonly abbreviated as MIG; this MIG designation as used hereinafter encompasses all hot wire welding processes. A "cold" welding filler wire is one which carries no current and which, though consumed, does not act as an electrode from which a welding arc is struck. In cold wire systems, the welding arc is struck between the workpiece and a nonconsumable permanent electrode. The cold welding filler wire is fed into the neighborhood of the arc, where a weld puddle is created. Many cold wire processes are of the Tungsten-Inert Gas type, commonly abbreviated as TIG; this TIG designation as used hereinafter encompasses all cold wire welding processes.) In both MIG systems and TIG systems an inert gas is supplied at the workpiece to insulate the weld puddle from ambient atmosphere thereby avoiding oxidation and contamination of the finished weld. Various welding filler wire feed systems are shown in U.S. Pat. Nos. 2,681,970; 2,880,305; 3,619,553; 3,652,823; and 3,808,397. The '970 patent relates to both MIG and TIG welding and it discloses both hot and cold welding filler wires. '970 illustrates feed of both hot and cold filler wires to the workpiece, at a constant speed, via a bulky nozzle through which the insulative welding gas also passes. There is no provision for varying feed speed or for starting and stopping welding wire feed at the nozzle, i.e. a fully automatic welding system is disclosed. The '305 patent relates to MIG welding and discloses a handpiece having both welding filler wire advancement wheels and a shielding gas outlet nozzle therein; this makes the handpiece bulky. The thrust of '305 is towards providing a bearing assembly which allows orderly unreeling of a welding filler wire from a stationary roll having its axis vertically oriented. The '553 patent relates to MIG welding and broadly discloses a handpiece through which hot welding wire is fed by a pair of drive wheels which advance the hot wire off a reel oriented with a vertical axis of rotation. There is no suggestion of any means for controlling off-on operation or rate of feed or the hot wire. The '823 patent discloses welding filler wire guide nozzles, which can handle either hot or cold filler wire, and is directed towards providing means for quick changeover among different sizes of welding wire and among welding wires of different materials. '823 uses a plurality of nozzles, each equipped with a different size or type of welding wire, to facilitate quick changeover. A common drive shaft is provided, with a plurality of separate feed rollers thereon, one roller for each of the wires to be fed. Feed is effected by shifting a counterroller into engagement over the selected wire and its associated feed roller. When this is done, the other wires remain loose on their rollers without pressure; those wires are not fed. The '823 patent shows drive and idler rollers used to advance welding filler wire and features nozzles removably received in clamps to maintain a selected angle between the wire feed nozzle and the position where the welding torch creates the weld puddle. '823 fails to disclose any means for controlling off-on operation or rate of feed of welding wire at a feed nozzle remote from the wire reel. The '397 patent discloses a control device to regulate welding current and voltage. The control device also allows welding rod to feed therethrough, but there is no indication of power feed for the flexible welding rod. The rod is gravity fed; this limits the applicability of '397 to heavy welding rod stock.
U.S. Pat. No. 3,248,525 discloses a welding wire fed from a spool, by drive rollers through a flexible conduit to a remote welding torch, with the torch-conduit connection made through a rotary coupling. '515 is directed primarily towards the conduit and the rotary coupling and does not disclose any means for varying wire feed speed or for starting and stopping wire feed.
These prior art devices tend to be heavy and cumbersome and do not facilitate regulation of welding filler wire feed rate at the work site. When a change in the characteristics of the workpiece being welded requires a change in the feed rate of the filler wire, the prior art devices necessitate shutdown of the welding system to be adjusted. Loss of welding efficiency results. Moreover, the cumbersome nature of the prior art devices does not allow a worker to easily weld in tight quarters or in awkward positions, e.g. lying flat on his back looking upward at the workpiece requiring welding. Additionally, previously known TIG devices are subject to frequent periods of downtime when the operator exhausts his supply of filler wire at the work site.